1. Field of Invention
The present invention relates to the field of integrated circuit (IC), and more particularly to a high-frequency bandwidth amplifier circuit.
2. Description of Related Arts
In different kinds of signal receivers (RF communications, optical communications, high-speed serial communications), the weak signals received are required to be further amplified, in order to facilitate processing the weak signal by the follow-up circuit. Along with the higher and higher signal frequency, the loss of signal is also growing in the process of transmission media. It is well known that the higher signal frequency requires the wider bandwidth of the amplified circuit, and the higher loss of signal requires the higher gain of the amplified circuit. The combination of these two aspects demands for amplifiers of higher and higher gain bandwidth product.
In the conventional high-frequency bandwidth amplifier circuit, basing on conventional structure that is topological invariant, in order to acquire higher gain bandwidth product, higher current and power loss is required. However, the gain bandwidth product is directly proportional to the square working current. This method demands to provide larger current, and also demands for larger power loss, which makes this method more and more unattractive. In addition, a small-sized amplifier can be used, to reduce the parasitic capacitance of the amplifier, for declining the influence on the bandwidth. However, the current driving capability of the small-sized amplifier is also very weak, and thus the amplifier cannot satisfy working requirement. Along with the further increased demand of the gain bandwidth product by the high-frequency bandwidth amplifier circuit, because of the limit of conventional topology, even if the current is further increased, the gain bandwidth product cannot be increased effectively. Thus, the improvement of the gain bandwidth product by the high-frequency bandwidth amplifier circuit falls into technological bottlenecks.
Therefore, it is necessary to provide a modified high-frequency bandwidth amplifier circuit to cover flaws which have been mentioned above.